Tensile force transmitting device, in particular a lifting device

ABSTRACT

A traction device, in particular devised as a lifting device, comprises a first engagement member (2) for engagement to a first coupling member, an intermediate portion (5) and a second end portion (6) adapted to form an attachment loop by the free end (7) of the end portion being, via a spring loaded locking member (12), releasably locked in a locking mechanism at the end of the intermediate portion adjacent the second end portion. The locking member is, through a connection arrangement (21), connected, in a tensile force transmitting manner, to a second engagement member (22), which is adapted for engagement to a second coupling member and which upon being subjected to a tensile force transmits this tensile force via the connection arrangement to the locking member and thereby releases the free end of the end portion.

FIELD OF INVENTION AND PRIOR ART

The invention is related to a tensile force transmitting elongateddevice, which primarily is intended to be used as a lifting device. Thedevice is suitably intended to have the character of a lifting strop atleast in part flexible. This is particularly suitable for timbertransportation by means of helicopter but may also be used for othertypes of load transports.

Since the beginning of the 1960's one has tried to transport timber bymeans of helicopter. All parties involved realize that such transportinvolves a very big market if it would be possible to carry outtransportation in an economical manner for the forest owner as well asthe helicopter company. There are today very large areas with goodtimber located so inaccessibly that it is difficult to be used in aneconomical manner with the means normally used for timbertransportation. The cost per hour for a helicopter is, however, veryhigh and the attempts until now carried out with helicopter based timbertransportation in association with use of ordinary lifting strops haveturned out to be economically doubtful, i.e. the transportation hasbecome too expensive for the forest owner and poorly paid for thehelicopter owner.

The lifting strops until now used in the attempts mentioned hereinabovewith helicopter transportation are steel wire or artificial fibrestrops, which all have in common that they are attached around the logby means of a running loop which when the strop is released from thehelicopter lifting hook remains around the log at the unloading locationand must be released by personnel on that location. Apart from this workbeing difficult and sometimes dangerous it has turned out to cause a lotof extra work for the helicopter since it must land to take on board theempty strops which must be brought back to the timber felling location.This extra stop in connection with the retransportation of the liftingstrops to the loading location cause the average time and accordinglythe rental cost when using helicopter transportation to be unacceptablyhigh and the profit correspondingly low. The requirement for personnelat the unloading location influences the overall economy negatively to ahigh degree.

SUMMARY OF THE INVENTION

The object of the invention is to devise an improved tensile forcetransmitting device, by means of which release of the load in questionmay occur without the entire device having to be released When using thedevice according to the invention as a lifting strop with helicoptertransportation, the helicopter need no longer land to bring with it theempty lifting strops, a fact which enables a considerable reduction ofthe time of use of the helicopter and a corresponding increase ofprofit; contributory to high profits is also the fact that no personnelis necessary at the unloading location.

This object is according to the invention achieved with the device moreclosely defined in appended claim 1. Preferable embodiments of thedevice according to the invention are defined in the other claims.

The main advantage when using the device according to the inventiondesigned as a lifting strop is that the load carried by the strop may bereleased therefrom with signal from the helicopter without need ofassisting personnel at the unloading location and the strop may, afterhaving released the load, directly accompany the helicopter back to thefelling location and be released thereon. The expenses for personnel arereduced at the same time as the helicopter gets a considerably improvedcontinuity in work than in previous attempts since it is no longernecessary to land to pick up the strop. Experiments carried out whileusing a helicopter of the type Bell 205 having a maximum load capacityof about 1900 kg have illustrated that it is possible, when using thelifting strop according to the invention, to carry out about 30 tripswith load per flying hour at a distance between loading and unloadinglocation of about 500 m and with about 2 m³ timber (about 1600 kg) perload. With such an efficient use of flying time it becomes economicallymotivated to use helicopter to transport timber from felling location toreloading location.

Various releasable and/or self-releasable lifting strop devices forvarious lifting purposes are previously known but they are not suitablefor the object intended to be solved by the present invention; inparticular, they are not suitable in connection with helicoptertransportation. As examples on such known lifting strops the U.S. Pat.Nos. 1,559,959 and 1,900,194 can be mentioned, which both are dependentupon a separate line for release, and the U.S. Pat. Nos. 2,813,744,4,181,342 and 2,385,338, which all are of a self-releasing type butwherein release is too unsafe for such lifting strop types to be used inpractise in connection with transportation of the kind mentionedhereinabove.

A locking mechanism is per se previously known by e.g. the U.S. Pat.2,323,914 but in connection with a parachute and without the new andoriginal features characterizing the device according to the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

With the reference to the appended drawings, a more specific descriptionof embodiment examples of the invention will follow hereinafter.

In the drawings:

FIG. 1 is a partly sectioned view illustrating the device according tothe invention in a locked condition, the left portion in FIG. 1illustrating the lower part of the device while the right portion ofFIG. 1 illustrates the upper part of the device,

FIG. 2 is a view similar to the left portion of FIG. 1 but illustratingthe device in a released condition,

FIG. 3 is a perspective view illustrating components of the lockingmechanism,

FIG. 4 is a view of a carrying device for the device in FIG. 1,

FIG. 5 is a view illustrating an alternative embodiment,

FIG. 6 is an enlarged view of a detail from the embodiment according toFIG. 5, and

FIG. 7 is a detailed view illustrating a further alternative.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The device according to the invention will hereinafter be described asforming a lifting strop. It comprises at a first, upper end portion 1, afirst engagement member 2 in the form of a loop adapted to be broughtinto engagement with a first coupling member 4 of a carrying device 3illustrated in FIG. 4. As appears for the rest in FIG. 1, the liftingstrop comprises an intermediate portion 5, which mainly is formed by aline or steel wire, and a lower end portion 6, e.g. in the form of achain, adapted to form an attachment loop about the load to be lifted.

One end of the chain 6 is attached to a bracket 7 secured, e.g. bywelding, to the shanks 8 of a fork like piece 9 which is in threadengagement with a sleeve 10, which internally houses a widened end piece11 on the lower end of the wire 5 and at the top abuts against an upperend wall of a sleeve 12. The sleeve 10 as well as the sleeve 12 comprisea central opening, through which the wire 5 passes. The free end ofchain 6 is provided with a securing member 13 comprising a portion 15adapted to be received in the slot shaped space 14 between the shanks 8of fork piece 9.

Sleeves 10 and 12 form parts of a locking mechanism co-operating withsecuring member 13. Sleeve 12 is in the embodiment arranged coaxiallyand externally to sleeve 10 and has the character of a locking sleeve.It is in the embodiment composed of an upper sleeve part 16 and a lowersleeve part 17 rigidly screwed into the upper sleeve part.

A spring 18, in the embodiment a screw compression spring, acts betweensleeves 10 and 12 so that space 14 in fork piece 9 connected to sleeve10 is actuated to be located at least partly surrounded by sleeve 12.The ends of spring 18 abut with pretensioning against an upper flange ofsleeve 10 and against a support rigidly secured relative to sleeve 12,said support being in the example formed by the upper end surface of thelower sleeve part 17.

The locking sleeve 12 is movable between a lower locking posiotion,which is illustrated in FIG. 1 and in which it is pressed downwardly byspring 18 so that sleeve 12 with its upper end wall abuts against thetop wall of sleeve 10 and thereby locks head portion 15 on lockingmember 13 within space 14, and an upper position, which appears fromFIG. 2 and in which sleeve 12 against the force from spring 18 is liftedso that slot space 14 is liberated and securing member 13 may beintroduced into or freely slide out of the space. The direction ofmovement of the securing member is sidewardly or obliquely downwardly.

In the locking position according to FIG. 1 a member 19 serves asobstruction against downward movement of securing member 13. Member 19is in the embodiment formed by a portion of a bolt 20 extending betweenshanks 8. As appears from FIG. 3, head portion 15 of the securing memberhas a plate like shape. Its side edges vertical in the locking positionaccording to FIG. 1 are parallel to the adjacent portions of sleeve 12and located relatively adjacent thereto so that head portion 15 bysleeve 12 is guided to maintain an upright position until substantiallythe entire slot 14 has been set free. It is pointed out that piece 9 notnecessarily must have the character of a fork since member 19 also couldbe designed in one piece therewith.

The spring 18 should not be more forceful than allowing the lockingsleeve 12 to be pulled into its upper position according to FIG. 2 byhand power in order to allow reintroduction of securing member 13 of thechain into slot 14.

Locking sleeve 12 is via a connection arrangement 21, which extendsalong the intermediate portion or wire 5 of the lifting strop, connectedin a tensile force transmitting manner to a second engagement member 22adapted for engagement with a second coupling member 23 (FIG. 4). In theembodiment according to FIGS. 1-4 engagement member 22 is formed by afurther loop extending to a point above loop 2 and being bigger than thelatter. At least one and in the embodiment two lines or wires 24 as wellas coupling pieces 25 and 26 are comprised in the connection arrangement21. Coupling piece 25 is permanently secured to locking sleeve 12 andpresents holes for penetration of wires 24, which at their ends havewidened pieces 26a. Coupling piece 26 comprises holes for the upper endsof wires 24 and also the latter are provided with widened end pieces 27.Loop 22 has its ends protruding through holes in coupling piece 26 andprovided with widened heads 28. The arrangement described formsaccordingly a tensile force transmitting connection between loop 22 andsleeve 12. The wire 5 passes movably through coupling pieces 25 and 26.

Along the flexible section of intermediate portion 5 and connectionarrangement 21, i.e. along wires 5, 24, these are surrounded by anelongated casing 29. This casing serves to hold the wires 5, 24 togetherand avoid that they inadvertently hook on to some object Casing 29 mayfor instance have the character of an elongated hose or stocking, whichat its upper and lower ends is attached relative to the connectionarrangement 21. This attachment may for instance be realized by windingtape indicated at 30 about casing 29 in its end areas so that casing 29is held relative to coupling pieces 25 and 26 or relative to wires 24above and under respectively the coupling pieces 25 and 26. Casing 29may be formed by fabric material, e.g. woven material It could also beformed by a plastic hose.

Wire 5 is surrounded by a tubular envelope 31, which as casing 29 isflexible Wires 24 are arranged externally of tube 31 and wire 5 islongitudinally displaceable within tube 31. The ends thereof are in themanner indicated in FIG. 1 received in seats in coupling pieces 25 and26. It may be preferable to secure the wires 24 relative to tube 31 inthe area between the ends of the wires, e.g. by winding adhesive tapebefore application of casing 29 about wires 24.

The carrying device illustrated in FIG. 4 comprises means 32, here inthe form of an eye, to be suspended from a helicopter via suitablecoupling equipment. The device comprises further a frame 33, to which aprotective cage 34 is secured. The coupling members 4 and 23 are bothformed by remotely releasable load hooks. More specifically the loadhooks may be released by the helicopter pilot for releasing each of theloops 2 and 22. Load hooks 4 and 23 are known per se and are forinstance accessible from the company Cargo Aids Limited, Bexhill-on-Sea,Sussex, England, under the designation SACRU SP 7109/3B and SACRU CA3000. The load hooks are releasable by being deliberated to pivotdownwardly so that loops 2 and 22 may slide off the hooks A newcharacteristicum for the carrying device 3 is, however, the location ofhooks 4, 23 at different levels in correspondence to the leveldifference between loops 2 and 22 and the design of load hooks 4, 23 sothat they are intended to simultaneously co-operate with two engagementmembers of the same lifting strop.

With helicopter based timber transportation, the lifting strop describedfunctions as follows:

The helicopter flies with the carrying device illustrated in FIG. 4 withthe electrically or otherwise releasable load hooks to the loadinglocation, where present personnel already have prepared the liftingstrops to be brought by the helicopter in the same lift so that theselifting strops each comprise a log attached in chain loop 6. With thehelicopter hovering above the ground, the lifting strops are with theirmain loops 2 hooked on to load hook 4 at the same time as the upperloops 22 of the lifting strops are hooked on to the upper load hook 23.The loop 22 of the lifting strops is so dimensioned that the entire loadvia loop 2 is transferred to hook 4 when each individual strop hangsfrom the carrying device 3 so that loop 22 accordingly is only retainedin upper load hook 23 without taking up any part of the load.

When all lifting strops intended to take part in the helicopter lift arecoupled to carrying device 3, the helicopter flies to the unloadinglocation, where the pilot at a suitable altitude above ground releasesthe lower load hook 4 of carrying device 3 so that this load hook setsthe main loop 2 of the lifting strop free with the result that the upperloop 22 takes over the load and accordingly via wires 21 pulls lockingsleeve 12 free from slot 14 in piece 9, which in its turn is actuateddownwardly by the weight of the log suspended in chain loop 6 until theposition according to FIG. 2 is reached, in which securing member 13 isdrawn out of slot 14 and liberates the log from the lifting strop. Withthe empty released lifting strop hanging via the upper loop 22 in theupper hook 23 the helicopter then flies back to the felling location,where the pilot releases hook 23 so that all lifting strops fall down onthe ground. During the intermediate time, the ground personnel hasprepared a new set of lifting strops for the next timber transportation,which occurs in the manner described above. While the helicopter is awaythe personnel uses the lifting strops from the preceding load forpreparing the next transportation and so on.

In the variant illustrated in FIGS. 5 and 6, the lifting stropcomprises, instead of the upper loop 22, a flange 35 connected in atensile force transmitting manner to coupling piece 26 and accordinglythe wires 24 via an upwardly directed extension of coupling piece 26. Aspreviously carrying device 3 (FIG. 5) comprises a releasable load hook 4for loop 2 of the lifting strop. Load hook 23 in the previous embodimentis, however, here replaced by a coupling member realized in the form ofgripping members 36, at least one of which and in the embodiment bothbeing movable so that the gripping members may hookingly engage underflange 35. The gripping members 36 are in the embodiment both pivotablymovable by means of power members 37. When loop 2 of the lifting strophangs in hook 4, the gripping portions of gripping members 36 arelocated somewhat below flange 35. When load hook 4 releases loop 2,gripping members 36 take over the carrying function in that flange 35engages the gripping members. Due to this chain sling 6 is released inthe manner previously described so that the log is set free. When thehelicopter has returned to the loading location, gripping members 36 areopened and thereby the carried lifting strops are set free and allowedto fall down on the ground. In FIG. 5 it is also indicated that chainsling 6 comprises means 38 known per se for varying the size of thesling.

The variant in FIG. 7 corresponds to the right portion in FIG. 1 withthe exception that loop 22 in FIG. 7 is arranged on a part 39, which isconnected in a tensile force transmitting but freely rotatable mannerrelative to connection arrangement 21 and coupling piece 26 containedtherein, which simplifies the loading procedure. More specifically, part39 surrounds a portion of coupling piece 26 and as previously, wire 5runs straight through the coupling piece.

The device described is of course not limited to the illustratedembodiment. Thus, it can be mentioned that the device of course may beused for lifting arbitrary loads. The device is for the rest not limitedonly to lifting but can be used for tensile force transmittancehorisontally as well as in sloping situations. As an example it can bementioned that the device could be used for towing, where the towingobject could comprise coupling members for engagement with engagementmeans 2; 22, 35 while the towed object could engage with attachment loop6. Further, the device according to the invention could be used forhoisting of various loads, e.g. timber in sloping terrain. Also othermodifications are conceivable within the scope of the invention.

I claim:
 1. A device for transmitting tensile force, in particular alifting device, comprising, at a first end portion, a first engagementmember (2) adapted for engagement with a first coupling member (4), anintermediate portion (5) and a second end portion (6) adapted to form anattachment loop by the free end (13) of the second end portion being, bymeans of a spring loaded locking member (12), releasably locked to alocking mechanism at the end of the intermediate portion adjacent thesecond end portion (6), the locking member (12) being, by means of aconnection arrangement (21) extending along the intermediate portion ofthe device, in a tensile force transmitting manner connected to a secondengagement member (22, 35), which is adapted for engagement with asecond coupling member (23, 36) and which upon being subjected totensile force transmits this tensile force via the connectionarrangement to the locking member (12) and thereby actuates the lockingmember to release the free end (13) of the second end portion so as toopen the attachment loop, the intermediate portion (5) and theconnection arrangement (21) being at least in part surrounded by anelongated casing (29), the intermediate portion (5) and the connectionarrangement (21) comprising an elongated flexible section and the casing(29) being flexible and surrounding said section.
 2. A device accordingto claim 1, wherein the first coupling member (4) for co-operation withthe first engagement member (2) is releasable while tensile force isbeing exerted on the device.
 3. A device according to claim 2, whereinthe first coupling member comprises a releasable load hook (4).
 4. Adevice according to claim 2, wherein the second engagement member (22,35) is adapted to take over the tensile force from the first engagementmember (2) upon releasing of the first coupling member (4) anddeliberation of the first engagement member (2) caused thereby.
 5. Adevice according to claim 4, wherein the second coupling member (23, 36)is releasable.
 6. A device according to claim 1, wherein theintermediate portion (5) at least in part is surrounded by andlongitudinally displaceable within a flexible envelope (31), theconnection arrangement (21) being arranged externally of the envelope(31).
 7. A device according to claim 1, wherein the spring loadedlocking member (12) is a sleeve, which in its locking position retains asecuring member (13) at the free end of the second end portion in aspace (14) at the end of the intermediate portion.
 8. A device accordingto claim 7, wherein the space (14) is located between two shanks (8) ofthe intermediate portion.